Bump actions/checkout from 5 to 6 (#109)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/push_gem.yml

@@ -27,7 +27,7 @@ jobs:
         with:
           egress-policy: audit
 
-      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
       - name: Set up Ruby
         uses: ruby/setup-ruby@eaecf785f6a34567a6d97f686bbb7bccc1ac1e5c # v1.237.0

.github/workflows/sync-ruby.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.repository_owner == 'ruby' }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Create GitHub App token
         id: app-token

.github/workflows/test.yml

@@ -34,7 +34,7 @@ jobs:
         git config --global core.autocrlf false
         git config --global core.eol lf
         git config --global advice.detachedHead 0
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Ruby ${{ matrix.ruby }}
       uses: ruby/setup-ruby@v1
       with: